Interpretive Summary: The western tarnished plant bug (Lygus) is an important pest of crops that has been extensively studied. Despite this effort, certain aspects of Lygus basic biology are poorly known. Among these are the factors regulating the adult diapause, which is a state of relative dormancy that facilitates survival through the winter. Daylength is known to play an import role in regulating diapause, but recent studies demonstrated the diapause response of Lygus changes after prolonged laboratory rearing. Because most research on Lygus diapause has used laboratory-reared insects, the validity of earlier reports of diapause in Lygus has been questioned. Laboratory reared insects are an important resource that can facilitate research on diapause so long as the insects exhibit a normal diapause response. Lygus originating as eggs from field-collected insects were reared in the laboratory for four generations to examine whether selected characteristics changed with rearing. Compared with the first generation of Lygus, the number of virgin females that laid eggs increased by the second generation, and the number of Lygus entering diapause decreased by the fourth generation. These results indicate that Lygus used in diapause research should be as close to the field population as possible, but no further removed than three generations. Results further show that the extent and timing of changes in laboratory-reared Lygus can differ for different biological characteristics. These findings emphasize the importance of understanding the influences of rearing on the specific biological characteristics under study, and the need to verify that laboratory-reared Lygus used in research have remained similar to their counterparts in nature.

Technical Abstract:
Several aspects of the basic biology of the western tarnished plant bug, Lygus hesperus Knight, are poorly known despite of the economic importance of this species. Among these are the factors regulating the adult diapause. Recent studies questioned the validity of earlier reports of diapause in L. hesperus, in part because of the demonstrated loss of diapause response in bugs obtained from long-standing laboratory colonies. However, use of laboratory reared bugs would facilitate additional diapause research so long as those bugs exhibit a diapause response similar to that of the field population. L. hesperus, originating as eggs from field-collected insects, were reared in the laboratory for four generations to examine corresponding changes in selected biological characteristics. Over the course of the four generations, incidence of diapause in both L. hesperus genders decreased whereas the frequency of oviposition by virgin females increased. Measurable changes were not observed in frequency of occurrence of a specific fat body type (glass bead fat) or nymphal development time. These results suggest L. hesperus used in diapause research should be as close to the field population as possible, but no further removed than three generations. Results further demonstrate variability among different biological characteristics in their responses to selection from laboratory rearing. Collectively, these findings demonstrate the importance of understanding the influences of rearing on specific biological characteristics under study, and the need to verify the similarity of laboratory-reared bugs to their native counterparts in studies used to draw inferences regarding the field population.